1. Field of the Invention
The present invention relates to a CT apparatus without a gantry, and in particular to a CT apparatus, without a gantry, for safety inspection.
2. Description of the Related Art
Application of CT technology to a safety inspection system is increasingly developed due to the superexcellent performance of CT technology in identification of substance density. However, since CT technology requires that data are acquired at different angles for data reconstruction, conventional X-ray radioscopy data are acquired at different angles by a gantry system rotating at a speed for reconstruction. Since rotary components are used, the apparatus has a complicated structure, loud operational noise, a great volume, and a high operation and maintenance cost. In recent years, with the increasing development of X-ray source technology, and especially with the advent of multi-beam X-ray sources based on carbon nanotube technology, new concepts are provided for data reconstruction at different angles in CT technology.
Triggering timing of ray emission focal spots of a carbon nanotube X-ray source is controlled in a time sequence. If the number of the ray emission focal spots of the X-ray source is enough, layout of receiving surfaces of a detector are effective, and timing control for emission and receiving is reasonable, sufficient quantity of data required for CT data reconstruction can be required for reconstruction in the CT technology independent of the rotary gantry system. With the advent of gantry-less CT technology, the problem of complicated data transmission confronted by the conventional CT technology is solved, and operational cost is lowered, and reliability is improved. However, since rotary components of a CT apparatus are eliminated by the gantry-less CT technology, the CT technology has higher requirements for layout of the ray source and detector of the CT apparatus. How to lay out the ray source and detector reasonably also becomes one of the difficulties confronted by gantry-less CT apparatus manufacturers.
The early gantry-less CT technology is generally applied in the field of medical inspection, the scanned object under inspection is relatively simple, and it can be ensured that the object is positioned at a constant position in a scanning passage. Therefore, in the commonest layout, the detector is laid out in the shape of a straight line or a circular are, and CT reconstruction data are acquired in different angle directions by relative movement of the ray emission focal spots of the multi-beam X-ray source relative to the receiving surface of the detector. In early gantry-less CT systems, the influence of the scanning passage on the layout of the X-ray source and detector, i.e., how to ensure that the scanning passage is large enough while an overall size of the gantry-less CT apparatus is small, is not synthetically considered whether in the straight line-shaped layout or a circular arc-shaped layout. Therefore, when the gantry-less CT apparatus is applied in the field of safety inspection, it has a large overall size and a low inspection rate so as to be far from meeting a floor space of the gantry-less CT apparatus required for quick inspection in the field of safety inspection. In the field of safety inspection, a size of the scanning passage, and a scanning speed are two important factors affecting inspection effect. Therefore, a CT apparatus for safety inspection has a scanning passage remarkably larger than a medical CT apparatus, and a CT apparatus for safety inspection has a speed remarkably faster than a medical CT system. Furthermore, most safety inspection apparatuses are located in public regions. Therefore, radiation shield requirements for the apparatus itself are high. These bring many rigorous requirements for the design of the safety inspection apparatus.